This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to Japanese Application No. 11(1999)-200021 filed on Jul. 14, 1999 and Japanese Application No. 2000-212515 filed on Jul. 13, 2000, the entire content of both of which is incorporated herein by reference.
The present invention generally relates to a driving force transmitting device for a vehicle. More particularly, the present invention pertains to a driving force transmitting device including a drive mode-shifting mechanism which shifts the drive mode between a two-wheel drive mode, a differential free four-wheel drive mode, and a differential lock four-wheel drive mode.
A conventional driving force transmitting device for a vehicle is disclosed in Japanese Patent Application Laid-Open Publication No. Hei 8 (1996)-85355. This device includes a first sleeve connected to the outer circumference of the right drive shaft and movable axially via a spline engagement, a second sleeve connected to the outer circumference of the first sleeve and axially movable via a spline engagement, a first dog-clutch device formed on the right side gear of the differential gear and the first sleeve to connect and disconnect the right side gear and the first sleeve in response to axial movement of the first sleeve, and a second dog-clutch device formed on the casing of the differential gear and the second sleeve to connect and disconnect the casing and the second sleeve in response to axial movement of the second sleeve. With this device, when the first sleeve is disconnected from the right side gear and the second sleeve is disconnected from the casing, the transmission of the driving force between the right and left drive shafts and the propeller or drive shaft is prohibited, and a two-wheel drive mode is thus established. When the first sleeve is connected to the right side gear and the second sleeve is disconnected from the casing, the transmission of the driving force between the right and left drive shafts and the drive shaft is allowed with functional operation of the differential gear, and so a differential-free four wheel drive mode is established. Further, when the first sleeve is connected to the right side gear and the second sleeve is connected to the casing, the transmission of the driving force between the right and left drive shafts and the drive shaft is allowed while prohibiting the functional operation of the differential gear, and so a differential-lock four wheel drive mode is established.
In the above-described device, however, two sleeves are required for shifting the drive mode between the three drive modes. Namely, the first sleeve shifts the drive mode between the two-wheel drive mode and the differential free four-wheel drive mode, and the second sleeve shifts the drive mode between the differential free four-wheel drive mode and the differential lock four-wheel drive mode under the first sleeve-on condition. Therefore, the number of the component increases and the complexity of the structure of the device is increased.
Further, because two actuators are required for operating the sleeves, the overall size of the system, including the transmitting device and the actuators, is increased and the manufacturing cost of the transmitting device is also increased.
In light of the foregoing, a need exists for a driving force transmitting device that does not suffer from the foregoing disadvantages and drawbacks.
It would thus be desirable to provide a driving force transmitting device for a vehicle which is able to shift the drive mode between three drive modes without increasing the manufacturing cost, the number of components and the complexity of the overall device.
According to one aspect of the present invention, a driving force transmitting device for a vehicle includes a housing in which are disposed a differential gear connected to a pair of wheels and a drive-mode-shifting mechanism. The drive-mode-shifting mechanism includes a first rotating member forming an output member of the differential gear for one wheel side, a second rotating member rotatable relative to the first rotating member and rotatable together with one of the wheels, a third rotating member rotatable together with a casing of the differential gear to which driving force is transmitted from a power source, and a movable member. The movable member is movable between a first position in which the first and the second rotating members are disconnected to effect the two-wheel-drive mode, a second position in which the first and the second rotating members are connected to effect the differential-free four-wheel-drive mode, and a third position in which the first, the second and the third rotating members are connected to effect the differential-lock four-wheel-drive mode.
When the movable member is positioned to disconnect the connection between the first and the second rotating members (i.e., the two-wheel-drive mode), the casing and the third rotating member rotate together in response to the driving force transmitted from the power source. An output member of the differential gear for another wheel side does not transmit the driving force from the power source to another wheel because the output member of the differential gear for one wheel side is disconnected from one wheel.
When the movable member is positioned to connect the first and second rotating members and disconnect the connection between the first and third rotating members (i.e., the differential-free four-wheel-drive mode), the third rotating member rotates together with the first and second rotating members, and the output member of the differential gear for another wheel side transmits power from the power source. In this mode, the difference in rotational speed between the one wheel and another wheel is absorbed because the first rotating member is connected with the output member of another wheel side through the differential gear. Furthermore, when the movable member connects the first and second rotating members and connects the first and third rotating members (i.e., the differential-lock four-wheel-drive mode), the pair of wheels rotates at the same rotation speed because the first, second and third rotating members are locked, and power is transmitted to the pair of wheels from the power source. Accordingly, it is possible to shift the drive mode between the two-wheel drive mode, the differential-free four-wheel-drive mode and the differential-lock four-wheel drive mode through the operation of the movable member.
According to another aspect of the present invention, a driving force transmitting device for a vehicle includes a housing in which are disposed a differential gear connected to a pair of wheels and a drive-mode-shifting mechanism. The drive-mode-shifting mechanism includes a first rotating member rotatable in response to the driving force transmitted from a power source, a second rotating member rotatable together with a casing of the differential gear, a third rotating member forming an output member for the differential gear and rotatable together with the one wheel, and a movable member shiftable between a first position in which the first and second rotating members are disconnected to effect the two-wheel-drive mode, a second position in which the first and second rotating members are connected to effect differential-free four-wheel-drive mode, and a third position in which the first and third rotating members are connected to effect the differential-lock four-wheel-drive mode.
When the movable member disconnects the connection between the first and second rotating members (i.e., the two-wheel-drive mode), the driving force from the power source is not transmitted to the pair of wheels because the driving force from the power source is not transmitted to the casing of the differential gear. When the movable member connects the first and second rotating members and disconnects the first and third rotating members (i.e., the differential-free four-wheel-drive mode), the driving force from the power source is transmitted to the pair of wheels through the differential gear, because the first rotating member rotates together with the casing through the second rotating member. In this mode, the difference in rotational speed between the one wheel and another wheel is absorbed by the differential gear. Further, when the movable member connects the first and second rotating members and connects the first and third rotating members (i.e., the differential-lock four-wheel-drive mode), the pair of wheels rotates at the same rotation speed because the first, second and third rotating members are locked and power from the power source is transmitted to the pair of wheels. Accordingly, it is possible to shift the drive mode between the two-wheel drive mode, the differential-free four-wheel drive mode and the differential-lock four-wheel drive mode by the operation of movable member.
In the present invention, it is possible to shift between the three drive modes by shifting a single movable member between the first position, the second position and the third position. Accordingly, the drive mode-shifting mechanism can be constructed and controlled in a rather simple manner. Further, it is possible to reduce the manufacturing cost of the drive mode-shifting mechanism.
The differential referenced herein refers to a differential assembly for absorbing the difference in rotational speed between the pair of wheels to permit smooth driving. The differential can be a limited slip differential. The final drive gearset referenced herein refers to the final drive/differential assembly.